Various applications require that the integrity of a sealed chamber be maintained to insure proper equipment operation. For example, for a housing intended to maintain a low internal pressure, a leak in the housing may allow ingress of gas that dilutes or contaminates the contents of the housing to the extent that housing contents are no longer useable for the intended purpose. In one particular application, the waveguide of a chip-scale atomic clock contains a selected vapor and requires that a predetermined rate of leakage be maintained to insure the pressure of the vapor and proper operation of the clock.